/**
 * 权重最小连接数
 */
module.exports = function (tasks, weightTotal, connectionsMap, context) {
    
    if (!tasks.length) return null;
    
    let min = tasks[0].weight, minIndex = 0, sum;
    
    const connectionsTotal = tasks.reduce((total, cur) => {
        total += (connectionsMap[cur.id] || 0);
        return total;
    }, 0);
    
    // algorithm: (weight + connections'weight) + random factor
    for (let i = 0; i < tasks.length; i++) {
        sum =
            (tasks[i].weight || 0) + (Math.random() * weightTotal) +
            (((connectionsMap[tasks[i].id] || 0) * weightTotal) / connectionsTotal);
        if (sum <= min) {
            min      = sum;
            minIndex = i;
        }
    }
    
    context.weightIndex += 1;
    context.weightIndex %= (weightTotal + 1);
    
    return tasks[minIndex];
};